Device identification and temperature sensor circuit

ABSTRACT

An integrated circuit includes a device identification circuit and a temperature sensor diode connected in parallel from a common node. The device identification circuit includes a resistor connected to a diode-connected transistor. The device identification circuit and the temperature sensor diode are adapted to not be simultaneously operating in an ON state. A first voltage is applied to the common node to place the device identification circuit in an ON state and place the temperature sensor diode in an OFF state to identify the integrated circuit. A second voltage is applied to the common node to place the device identification circuit in an OFF state and place the temperature sensor diode in an ON state to determine a temperature of the integrated circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application61/529,287 filed on Aug. 31, 2011 and U.S. Provisional Application61/529,288 filed on Aug. 31, 2011.

TECHNICAL FIELD

The present invention relates generally to integrated circuits, and moreparticularly to an integrated circuit that includes a deviceidentification and temperature sensor circuit.

BACKGROUND

Performance of an integrated circuit, such as an image sensor, can bedependent on the temperature. For example, dark current inside an imagesensor is highly temperature dependent. The dark current will increasewith an increase of temperature and higher dark current degrades theperformance of the image sensor. Higher dark current impacts the dynamicrange of the image sensor, the dark reference level, and can causevarious defects in captured images. If the temperature becomes too high,the sensor is susceptible to permanent damage.

One conventional technique for measuring the temperature of an imagesensor is to mount a thermal couple on the package of the image sensor,either at the front side or at the back side of the package, dependingon how the sensor is mounted on the circuit board. The thermal couplecan occupy a lot of space and make a camera or other image capturedevice bulky. Also, over time, the epoxy used to affix the thermalcouple to the package can age and become loose. And the temperaturetypically cannot be measured until the loose epoxy is repaired.

SUMMARY

An integrated circuit includes a device identification circuit and atemperature sensor diode connected in parallel. The deviceidentification circuit includes a resistor connected to adiode-connected transistor. The device identification circuit and thetemperature sensor diode are adapted to not be operating in an ON statesimultaneously. The resistor is connected between the diode-connectedtransistor and a reference voltage. The temperature sensor diode isconnected to either the same reference voltage or a different referencevoltage. The device identification circuit has a first polarity and thediode-connected transistor a different second polarity, where polarityis defined as a positive voltage change or a negative voltage changerelative to the respective reference voltage.

A system to identify a device and to measure a temperature of the deviceincludes a power supply, a device identification circuit, and atemperature sensor diode. The device identification circuit includes aresistor connected between a diode-connected transistor having a firstpolarity and the first reference voltage. The temperature sensor diodehas a second polarity and is connected between the power supply and asecond reference voltage. The power supply can be disposed, for example,in an image capture device and the device identification circuit and thetemperature sensor diode in an image sensor. A processor included in theimage capture device can use the device identification circuit toidentify the type of image sensor. The processor can also continuouslyor periodically monitor or determine the temperature of the imagesensor.

A method for identifying an integrated circuit and determining atemperature of the integrated circuit uses a circuit that includes adevice identification circuit having a resistor connected to adiode-connected transistor and further includes a temperature sensordiode connected in parallel with the device identification circuit. Thedevice identification circuit and the temperature sensor diode areconnected to a common node. The method includes applying a first voltageto the common node to place the device identification circuit in an ONstate and place the temperature sensor diode in an OFF state to identifythe integrated circuit. A second voltage can be applied to the commonnode to place the device identification circuit in an OFF state andplace the temperature sensor diode in an ON state to determine atemperature of the integrated circuit.

The integrated circuit can be identified by determining a resistancevalue of the resistor included in the device identification circuit, anddetermining a corresponding resistance value to the determinedresistance value. The corresponding resistance value can be included inknown resistance values for different integrated circuits.

The temperature of the integrated circuit can be determined by measuringa current value through the temperature sensor diode, comparing themeasured current value against a plurality of predetermined currentvalues determined at different temperatures, and determining thetemperature of the integrated circuit by determining one of thepredetermined current values in the plurality of current values thatcorrespond with the measured current value.

The temperature of the integrated circuit can be determined by measuringa voltage value across the temperature sensor diode, comparing themeasured voltage value against a plurality of predetermined voltagevalues determined at different temperatures, and determining thetemperature of the integrated circuit by determining one of thepredetermined voltage values in the plurality of voltage values thatcorrespond with the measured current value.

ADVANTAGEOUS EFFECT

The present invention implements both a device identification featureand a temperature sensor feature on a single integrated circuit withoutintroducing an extra bond pad or package pin. Manufacturers of productsthat currently use either one of the features can utilize both featureswith minimum modifications to the current electronics. Integratedcircuits, such as image sensors, having unique features can use thedevice identification feature to automatically identify an integratedcircuit and implement or optimize settings, programs, and operatingconditions based on the specification of the identified integratedcircuit. The device identification feature allows manufacturers todesign a single system that is able to work for different integratedcircuits or devices. Additionally, the temperature sensor feature can beused to periodically or continuously monitor the temperature of theintegrated circuit and prevent device failures when the temperature ofthe integrated circuit becomes too high. It can also be used to performsome image improvement algorithms such as, for example, dark currentsubtraction at different temperatures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are better understood with reference to thefollowing drawings. The elements of the drawings are not necessarily toscale relative to each other.

FIG. 1 is a schematic diagram of a device identification and temperaturesensor circuit in an embodiment in accordance with the invention;

FIG. 2 illustrates examples of I-V curves of a PN-junction diode atdifferent temperatures in an embodiment in accordance with theinvention;

FIG. 3 is a cross-sectional view of a portion of a first integratedcircuit that includes device identification and temperature sensorcircuit 100 in an embodiment in accordance with the invention;

FIGS. 4 and 5 are schematic diagrams depicting one example of anexternal circuit connected to device identification and temperaturesensor circuit 100 shown in FIG. 1;

FIG. 6 is a simulated I-V curves based on the circuit shown in FIGS. 4and 5 in an embodiment in accordance with the invention;

FIG. 7 depicts a relationship between diode current and temperaturealong line A-A in FIG. 6 in an embodiment in accordance with theinvention;

FIG. 8 depicts a relationship between diode current and temperature fordifferent voltages at different temperatures obtained along line B-B inan embodiment in accordance with the invention;

FIG. 9 depicts the relationship between the diode current and the diodetemperature when the current is at the particular current represented byline B-B in FIG. 8;

FIG. 10 is a cross-sectional view of a portion of a second integratedcircuit that includes device identification and temperature sensorcircuit 100 in an embodiment in accordance with the invention; and

FIG. 11 is a simplified block diagram of an image capture device in anembodiment in accordance with the invention.

DETAILED DESCRIPTION

Throughout the specification and claims the following terms take themeanings explicitly associated herein, unless the context clearlydictates otherwise. The meaning of “a,” “an,” and “the” includes pluralreference, the meaning of “in” includes “in” and “on.” The term“connected” means either a direct electrical connection between theitems connected or an indirect connection through one or more passive oractive intermediary devices. The term “circuit” means either a singlecomponent or a multiplicity of components, either active or passive,that are connected together to provide a desired function. The term“signal” means at least one current, voltage, or data signal.

Additionally, directional terms such as “on”, “over”, “top”, “bottom”,are used with reference to the orientation of the Figure(s) beingdescribed. Because components of embodiments of the present inventioncan be positioned in a number of different orientations, the directionalterminology is used for purposes of illustration only and is in no waylimiting. When used in conjunction with layers of an integrated circuitwafer or corresponding integrated circuit, the directional terminologyis intended to be construed broadly, and therefore should not beinterpreted to preclude the presence of one or more intervening layersor other intervening integrated circuit features or elements. Thus, agiven layer that is described herein as being formed on or formed overanother layer may be separated from the latter layer by one or moreadditional layers.

And finally, the term “substrate” is to be understood as asemiconductor-based material including, but not limited to, silicon,silicon-on-insulator (SOI) technology, doped and un-dopedsemiconductors, epitaxial layers formed on a semiconductor substrate,and other semiconductor structures.

Referring to the drawings, like numbers indicate like parts throughoutthe views.

FIG. 1 is a schematic diagram of a device identification and temperaturesensor circuit in an embodiment in accordance with the invention. Deviceidentification circuit 101 is connected in parallel with temperaturesensor diode 106. Device identification circuit 101 and temperaturesensor diode 106 are connected to common node 108. Device identificationcircuit 101 and temperature sensor diode 106 are also connected toreference voltages 109, 111. The reference voltages can be one commonvoltage, such as ground, or two different voltages.

Device identification circuit 101 includes diode-connected transistor102 connected in series with resistor 104. Temperature sensor diode 106is implemented as a PN junction diode and diode-connected transistor 102as a diode-connected metal-oxide-semiconductor field-effect transistor(MOSFET) in an embodiment in accordance with the invention.Additionally, the impedance of diode-connected transistor 102 is smallerthan the resistance value of resistor 104 in an embodiment in accordancewith the invention.

The anode of temperature sensor diode 106 is connected to the referencevoltage 109 which can be ground as shown or other reference voltages.The cathode is connected to common node 108. Common node 108 isconnected to bond pad 110. The forward current across diode 106 isdependent upon temperature. The Shockley diode equation relates thediode current I of a PN junction diode to the diode voltage V. Thisrelationship is known as the diode I-V characteristic, which can becharacterized by the equation,

$\begin{matrix}{I = {I_{s}\left( {{\mathbb{e}}^{\frac{qV}{nkT}} - 1} \right)}} & {{Equation}\mspace{14mu} 1}\end{matrix}$where I is the forward current through the diode, I_(s) is the reversebias saturation current, V is the voltage across the diode, T istemperature of the PN junction in Kelvins, and n is a junction constant(typical around 2 for diode). The letters q and k represent constants,where k is Boltzmann's constant (1.38E-23 joules/Kevin) and q is themagnitude of charge on an electron (1.6E-19 coulombs).

The reverse saturation current can be defined by the equation,

$\begin{matrix}{I_{s} = {I_{c}{\mathbb{e}}^{- \frac{{qE}_{g}}{nkT}}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$where I_(c) is a current constant and E_(g) is the diode materialbandgap (1.12 eV for silicon).

From Equations 1 and 2, diode I-V curves versus temperature can becalculated and plotted, as shown in FIG. 2. Three I-V curves fortemperatures of 0° C., 50° C., and 100° C. are illustrated in FIG. 2.The three I-V curves show the forward current through a diode increaseswith temperature.

Referring now to FIG. 3, there is shown a cross-sectional view of afirst integrated device including device identification and temperaturesensor circuit 100 in an embodiment in accordance with the invention. Awell 302 is disposed in substrate 304. Well 302 is a p-type well andsubstrate 304 an n-type substrate in an embodiment in accordance withthe invention.

Temperature sensor diode 106 is formed between p-type well 302 and ann-type well 306 disposed in p-type well 302. The anode of the diode 106is connected to a ground through a contact (not shown) in p-selectregion 308. The cathode of diode 106 is connected to bond pad 110through a contact in n-select region 310. N-select region 310 isdisposed in n-type well 306.

Diode-connected transistor 102 is also built in p-type well 302 with thesource region 312 and drain region 314 of transistor 102 disposed inp-type well 302. Source region 312 and drain region 314 are n-typeregions in an embodiment in accordance with the invention. The gate 316of diode-connected transistor 102 is tied to drain region 314, and boththe gate 316 and drain region 314 are connected to bond pad 110. Sourceregion 312 is connected to one end of resistor 104. The other end ofresistor 104 is connected to the same ground that is connected totemperature sensor diode 106 through a contact in p-select region 308.Resistor 104 is made of polysilicon material in an embodiment inaccordance with the invention.

In the illustrated embodiment, one or more additional circuits orcomponents 318, 320 are constructed in or on well 322. Well 322 is ap-type well in an embodiment in accordance with the invention. A currentflows through p-type well 302 into n-type well 306 when diode 106 isforward-biased. The size of temperature diode 106 can be much largerthan the size of the transistor 102 to minimize the impact of thecurrent flow from the transistor 102 when the bond pad is applied anegative voltage. The p-type wells 302 and 322 can be formed separatelyto prevent the diode current from affecting the performance of the oneor more additional circuits or components 318, 320. In addition, diode106 and resistor 104 can both be connected to a reference level otherthan ground, or connected separately to two different reference levelsincluding ground.

FIG. 4 is a schematic diagram depicting one example of an externalcircuit connected to bond pad 110 shown in FIG. 1. Power supply 400supplies a positive voltage V_(dc) to bond pad 110 through a knownresistor 402 (R1). The positive voltage at the cathode of temperaturesensor diode 106 turns off the diode and turns on diode-connectedtransistor 102. The actual turn-on voltage of diode-connected transistor102 depends upon the characteristics of diode-connected transistor 102,including the threshold voltage V_(t). Diode-connected transistor 102turns on because gate 316 and drain 314 are tied together. Therefore, acurrent I₀ flows only through diode-connected transistor 102 andresistor 104. The current I₀ is equal to V₁/R₁, where V₁ is the voltageacross resistor 402 and R₁ is the resistance value of resistor 402.Since the impedance R2 of diode-connected transistor 102 issignificantly smaller than the resistance value of resistor 104 in oneembodiment, the voltage drop V₂ across diode-connected transistor 102 isnegligible compared to the voltage drop V₀ across device identificationresistor 104. Therefore, the resistance value of device identificationresistor 104 can be calculated with the equation (V_(dc)−V₁)/I₀, orR₁*(V_(dc)−V₁)/V₁. Alternatively, in another embodiment, when theimpedance R2 of transistor 102 is comparable to the resistance value ofresistor 104, the resistance value of device identification resistor 104can be calculated with the equation (V_(dc)−V₁V2)/I₀, orR₁*(V_(dc)−V₁)/V₁−R2.

An integrated circuit that uses a device identification and temperaturesensor circuit can be designed to have a specific resistance value forresistor 104. Individual integrated circuits have specific unique deviceidentification resistance values for resistor 104. If a calculatedresistance value for resistor 104 matches or substantially matches aknown resistance value of an integrated circuit within a statisticalmargin of error, the identity or type of the integrated circuit can bedetermined based on the match between the calculated value and the knownvalue of resistor 104. The known resistance value can be included in alist of predetermined resistance values for a variety of integratedcircuits. By way of example only, the list can be implemented as alookup table stored in a memory. An apparatus that includes theidentified integrated circuit can then automatically select the correcthardware or software configuration for the identified integratedcircuit, or perform operations specific for that integrated circuit.

The operation of using the temperature sensor to measure temperature isshown in FIG. 5. When a negative voltage (−V_(dc)) is applied from powersupply 400, the negative voltage will turn off diode-connectedtransistor 102 and prevent any current flow along the path of the deviceidentification circuit which includes resistor 104. In the meantime, thenegative voltage at the cathode of temperature sensor diode 106 willplace the diode in a forward-biased state and a forward current I₁ willflow through diode 106 and through resistor 402. The current I₁ flowingthrough resistor 402 is calculated by V₁/R₁, where V₁ is the voltageacross resistor 402 and R₁ is the resistance value of resistor 402.Since the drain region of the transistor 102 is n-type and the drainregion is built inside a p-type well, there will be a forward-biasedcurrent flowing into the bond pad 110 as well when a negative voltage isapplied from the power supply 400. Because the size of the temperaturediode is much larger than the transistor 102 in one embodiment, thecurrent flowing from the drain region of the transistor 102 is muchsmaller than the current flowing from the temperature diode. Therefore,the current I₁ is close to the current flowing through temperaturesensor diode 106. The voltage V₃ across temperature sensor diode 106 canthen be calculated by subtracting V₁ from (−V_(dc)). Therefore, sincethe relationship between I₁ and V₃ across temperature sensor diode 106is temperature dependent, the temperature can be determined by comparingthe data set (I₁, V₃) with data sets determined at differenttemperatures. The data sets are pre-determined and stored in a memory(not shown) in an embodiment in accordance with the invention. By way ofexample only, the pre-determined data sets can be stored in a look-uptable, which is described in more detail in conjunction with FIGS. 6-9.

Device identification and temperature sensor circuit is designed so thatonly one of the two elements in circuit 100 is turned on and operatingat any given time. The threshold voltage of the diode-connectedtransistor 102 is designed to be positively away from zero in anembodiment in accordance with the invention. For example, the thresholdvoltage can be designed to be one volt above the zero, so that theimpact of the leakage current of diode-connected transistor 102 upon thetemperature measurement is small and insignificant when the voltagebecomes negative. One method to increase the threshold voltage ofdiode-connected transistor 102 is to implant a different type of dopantinto the channel. For a NMOS transistor, the dopant can be boron in anembodiment in accordance with the invention.

The device identification circuit 101 and the temperature sensor 106 areadapted such that only one circuit is operating in an ON state when theother circuit is in an “OFF” state. The device identification circuit101 and the temperature sensor diode 106 are adapted such that bothcircuits are not simultaneously operating in an ON state. When a circuitis in the “OFF” state, the impact or effect of the circuit in the “OFF”state on the circuit in the “ON” state is minimized. The circuit in the“ON” state is in a state where the circuit will be used to determine atemperature, or to determine a voltage or current for identificationpurposes. The device identification circuit 101 has a first polarity andthe temperature sensor has a second different polarity, where polarityis defined as a positive voltage change or a negative voltage changerelative to a reference voltage.

Once a device is identified using the device identification circuit 101,temperature sensor diode 106 can periodically or continuously monitorthe temperature of the integrated circuit while the integrated circuitis operating. For example, when the integrated circuit is an imagesensor that is included in a security camera, the security camera canmonitor the temperature of the image sensor while capturing images orvideo. If the temperature of the image sensor rises above a thresholdindicating the temperature is too high, the camera can shut downautomatically for a period of time to prevent damage to the image sensordue to high temperature.

FIG. 6 illustrates simulated I-V curves that are based on the circuitshown in FIGS. 4 and 5. One method that can be used to determine thetemperature of an integrated circuit using temperature sensor diode 106is to compare different current values obtained at a constant voltage.The current values at different temperatures are obtained along thevertical line A-A when the voltage is constant at −0.7V. FIG. 7 showsthe relationship between the diode current and the temperature when thevoltage is at −0.7V in an embodiment in accordance with the invention.The current values in curve 700 can be compared against a measuredcurrent and the temperature of the integrated device is determined bymatching or identifying a corresponding current value with the measuredcurrent.

The current values can be included in a look-up table saved in a memory.For example, if the integrated circuit is an image sensor, the look-uptable can be saved in a memory in an image capture device. When thetemperature is to be measured, the diode current can be calculated usingthe method described earlier. Then the temperature of the image sensorcan be obtained by matching the diode current with one of the diodecurrents stored in the lookup table. If a current falls in between twocurrent values in the look-up table, a linear interpretation will beperformed to get the temperature value in an embodiment in accordancewith the invention.

Another method that can be used to determine temperature is to comparedifferent voltages at a constant current. FIG. 8 depicts a relationshipbetween diode current and temperature for different voltages atdifferent temperatures obtained along line B-B in an embodiment inaccordance with the invention. The voltage values at differenttemperatures are obtained along the vertical line B-B when the currentof the power supply is constant at −0.002 A. FIG. 9 shows therelationship between the diode voltage and the diode temperature whenthe current is −0.002 A. Therefore, when the temperature is to bemeasured, the diode voltage can be calculated using the method describedearlier and the temperature of the image sensor can be obtained bymatching or determining a corresponding voltage value stored in thelookup table with the calculated diode voltage. If a voltage falls inbetween two voltage values, a linear interpretation will be performed toget the temperature value in an embodiment in accordance with theinvention.

Temperature sensor diode 106 and diode-connected transistor 102 aredesigned so that when diode-connected transistor 102 is in an ON state,the leakage current from temperature sensor diode 106 is small comparedto the current I₀ flowing through the diode-connected transistor 102 andresistor 104 in an embodiment in accordance with the invention. Inaddition, transistor 102 has lower impedance compared to the resistancevalue of resistor 104, allowing the calculation of the resistance ofresistor 104 to be accurate.

FIG. 10 is a cross-sectional view of a portion of a second integratedcircuit that includes device identification and temperature sensorcircuit 100 in an embodiment in accordance with the invention. Theintegrated circuit shown in FIG. 10 is identical to the integratedcircuit of FIG. 3 except the p-type well 302 in FIG. 3 is replaced withtwo separate individual p-type wells 1000 and 1002. The p-type well 1000is used to form the temperature sensor diode 106 and the p-type well1002 is used to form the diode-connected transistor 102. The separatewells 1000, 1002 can reduce the crosstalk between the temperature sensordiode 106 and diode-connected transistor 102. The temperature sensordiode 1004 is formed by the p-type well 1000 and n-select region 1006.Both p-wells 1000, 10002 are tied to ground through p-select region 308.Referring now to FIG. 11, there is shown a simplified block diagram ofan image capture device in an embodiment in accordance with theinvention. Image capture device 1100 is implemented as a digital camerain FIG. 11. Those skilled in the art will recognize that a digitalcamera is only one example of an image capture device that can utilizean image sensor incorporating the present invention. Other types ofimage capture devices, such as, for example, cell phone cameras, digitalvideo camcorders, and other hand-held devices can be used with thepresent invention.

In digital camera 1100, light 1102 from a subject scene is input to animaging stage 1104. Imaging stage 1104 can include conventional elementssuch as a lens, a neutral density filter, an iris and a shutter. Light1102 is focused by imaging stage 1104 to form an image on image sensor1106. Image sensor 1106 captures one or more images by converting theincident light into electrical signals. By way of examples only, imagesensor 1106 can be implemented as a CCD image sensor or a CMOS imagesensor. Image sensor 1106 includes device identification and temperaturesensor circuit 100 shown in FIG. 1.

Digital camera 1100 further includes processor 1108, memory 1110,display 1112, and one or more additional input/output (I/O) elements1114. Although shown as separate elements in the embodiment of FIG. 11,imaging stage 1104 may be integrated with image sensor 1106, andpossibly one or more additional elements of digital camera 1100, to forma compact camera module.

Processor 1108 may be implemented, for example, as a microprocessor, acentral processing unit (CPU), an application-specific integratedcircuit (ASIC), a digital signal processor (DSP), or other processingdevice, or combinations of multiple such devices. Various elements ofimaging stage 1104 and image sensor 1106 can be controlled by timingsignals or other signals supplied from processor 1108.

Memory 1110 can be configured as any type of memory, such as, forexample, random access memory (RAM), read-only memory (ROM), Flashmemory, disk-based memory, removable memory, or other types of storageelements, in any combination. Memory 1110 can store the list of knownresistance values and integrated circuits that correspond to theresistance values that can be used when identifying an integratedcircuit.

A given image captured by image sensor 1106 may be stored by processor1108 in memory 1110 and presented on display 1112. Display 1112 istypically an active matrix color liquid crystal display (LCD), althoughother types of displays may be used. The additional I/O elements 1114may include, for example, various on-screen controls, buttons or otheruser interfaces, network interfaces, or memory card interfaces, or evenvoice command controls.

Driver circuit 1116 includes a power supply and a resistor (not shown)in an embodiment in accordance with the invention. The power supply andresistor can be implemented as V_(DC) and resistor 402 shown in FIGS. 4and 5. Thus, the power supply is used to apply voltages to common node108 (FIG. 1).

Processor 1108 controls driver circuit 1116 to either calculate aresistance value of the resistor (i.e., resistor 104 in FIG. 1) indevice identification circuit by sourcing a positive voltage or tomeasure the temperature of image sensor 1106 by sourcing a negativevoltage. Once the resistance value of the resistor (i.e., resistor 104)in the device identification circuit is determined, processor 1108 canrecognize image sensor 1106 and set up the correct camera file andtiming for image sensor 1106 automatically. By controlling drivercircuit 1116, processor 1108 can continuously or periodically monitorthe temperature of image sensor 1106 using device identification andtemperature sensor circuit 100 and pre-determined data sets stored inmemory 1110. Based on the temperature measured, processor 1108 cancontrol driver circuit 1116 to operate the image sensor 1106accordingly. For example, if the temperature of image sensor 1106 is toohigh, processor 1108 can control driver circuit 1116 to turn off thepower supply to the image sensor 1106 to prevent any damage to imagesensor 1106 or to start a cooling process if there is a cooler attachedto image sensor 1106. In addition, processor 1108 can perform one ormore algorithms to improve the image quality related to the temperature.One example of an algorithm is to subtract dark current based on thetemperature measurement from image signals since the dark current in theimage sensor 1106 increases with temperature.

It is to be appreciated that the digital camera shown in FIG. 11 maycomprise additional or alternative elements of a type known to thoseskilled in the art. For example, a thermoelectric cooling unit can beattached on the back of the image sensor 1106 inside the digital camera.The cooling unit can be used to cool the image sensor whenever it isneeded based on the temperature reading. Elements not specifically shownor described herein may be selected from those known in the art. Asnoted previously, the present invention may be implemented in a widevariety of image capture devices. Also, certain aspects of theembodiments described herein may be implemented at least in part in theform of software executed by one or more processing elements of an imagecapture device. Such software can be implemented in a straightforwardmanner given the teachings provided herein, as will be appreciated bythose skilled in the art.

The invention has been described in detail with particular reference tocertain embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention. For example, the structure of the device identification andtemperature sensor circuit has been described as having certainconductivity types. In particular, an NMOS transistor 102 built in ap-type well. However, other embodiments in accordance with the inventionare not limited to this construction. The conductivity types can bereversed in other embodiments.

The identification resistor is described as made by polysiliconmaterial, it is understood that other materials can also be used to makethe resistor. In addition, both device identification resistor andtemperature sensor are connected to ground, it is understood they can betied to other reference voltage as well.

And even though specific embodiments of the invention have beendescribed herein, it should be noted that the application is not limitedto these embodiments. In particular, any features described with respectto one embodiment may also be used in other embodiments, wherecompatible. And the features of the different embodiments may beexchanged, where compatible.

1. An integrated circuit includes a device identification circuit thatincludes a resistor connected to a diode-connected transistor; and atemperature sensor diode connected in parallel with the deviceidentification circuit, where the device identification circuit and thetemperature sensor diode are adapted to not be simultaneously operatingin an ON state. The impact or effect of the circuit in an “OFF” state onthe circuit in the “ON” state is minimized.

2. The integrated circuit as in clause 1 where the integrated circuitcomprises an image sensor.

3. An integrated circuit includes a device identification circuit thatincludes a resistor connected between a diode-connected transistor and afirst reference voltage, where the diode-connected transistor has afirst polarity applied to the first reference voltage; and a temperaturesensor diode connected in parallel with the device identificationcircuit and having a second polarity applied to a second referencevoltage.

4. The integrated circuit as in clause 3 where the integrated circuitcomprises an image sensor.

5. A system to identify a device and to measure a temperature of thedevice, the system including a power supply electrically connected to acommon node; a device identification circuit connected between thecommon node and a first reference voltage, where the deviceidentification circuit includes a diode-connected transistor connectedto a resistor with the diode-connected transistor having a firstpolarity and connected to the common node and the resistor connectedbetween the diode-connected transistor and the first reference voltage;and a temperature sensor diode having a second polarity connected inparallel with the device identification circuit, where the temperaturesensor diode is connected between the common node and a second referencevoltage.

6. The system as in clause 5 further including a second resistorconnected between the power supply and the common node.

7. The system as in clause 6 where the power supply and the secondresistor are disposed in an image capture device.

8. The system as in clause 7 where the device identification circuit andthe temperature sensor diode are disposed in an image sensor.

9. The system as in clause 5 further including a processor connected tothe integrated circuit; a memory connected to the processor; and adriver circuit connected to the processor and to the integrated circuit.

10. A method for identifying an integrated circuit and determining atemperature of the integrated circuit using a circuit comprising deviceidentification circuit that includes a resistor connected to adiode-connected transistor and a temperature sensor diode connected inparallel with the device identification circuit, where the deviceidentification circuit and the temperature sensor diode are connected toa common node, the method including applying a first voltage to thecommon node to place the device identification circuit in an ON stateand place the temperature sensor diode in an OFF state; identifying theintegrated circuit; applying a second voltage to the common node toplace the device identification circuit in an OFF state and place thetemperature sensor diode in an ON state; and determining a temperatureof the integrated circuit.

11. The method as in clause 10, where identifying the integrated circuitincludes determining a resistance value of the resistor included in thedevice identification circuit; and determining a correspondingresistance value from a plurality of predetermined resistance values fordifferent integrated circuits to the resistance value of the resistor.

12. The method as in clause 10 where determining a temperature of theintegrated circuit includes measuring a current value through thetemperature sensor diode; comparing the measured current value against aplurality of predetermined current values determined at differenttemperatures; and determining the temperature of the integrated circuitby determining one of the predetermined current values in the pluralityof current values that correspond with the measured current value.

13. The method as in clause 10 where determining a temperature of theintegrated circuit includes measuring a voltage value across thetemperature sensor diode; comparing the measured voltage value against aplurality of predetermined voltage values determined at differenttemperatures; and determining the temperature of the integrated circuitby determining one of the predetermined voltage values in the pluralityof voltage values that correspond with the measured current value.

14. The method as in clause 10 where the integrated circuit comprises animage sensor.

PARTS LIST

-   100 device identification and temperature sensor circuit-   101 device identification circuit-   102 diode-connected transistor-   104 resistor-   106 temperature sensor diode-   108 common node-   109 reference voltage-   110 bond pad-   111 reference voltage-   300 integrated circuit-   302 well-   304 substrate-   306 well-   308 region-   310 region-   312 source region-   314 drain region-   316 gate of transistor-   318 other circuit or component-   320 other circuit or component-   322 well-   400 power supply-   402 resistor-   1000 well-   1002 well-   1004 temperature sensor diode-   1006 region-   1100 image capture device-   1102 light-   1104 imaging stage-   1106 image sensor-   1108 processor-   1110 memory-   1112 display-   1114 other input/output (I/O) elements-   1116 driver circuit

The invention claimed is:
 1. An integrated circuit, comprising thereon:a bond pad configured to receive a first signal and a second signaldifferent than the first signal; a device-identification circuit foridentifying the integrated circuit, the device-identification circuithaving a first polarity and being coupled to the bond pad; and atemperature sensor connected in parallel with the device-identificationcircuit for determining a temperature of the integrated circuit, thetemperature sensor having a second polarity that is different than thefirst polarity and being coupled to the bond pad; thedevice-identification circuit being configured to operate in response tothe second signal and the temperature sensor being configured to benonoperational in response to the second signal; and the temperaturesensor being configured to operate in response to the first signal andthe device identification circuit being configured to be nonoperationalin response to the first signal.
 2. The integrated circuit of claim 1,wherein the device-identification circuit comprises a resistor connectedto a diode-connected transistor.
 3. The integrated circuit of claim 2,wherein the temperature sensor is a diode.
 4. The integrated circuit ofclaim 1, wherein the integrated circuit comprises an image sensor. 5.The integrated circuit of claim 1, wherein the first signal is a voltageand the second signal is a voltage.
 6. The integrated circuit of claim1, wherein the first signal is a positive voltage and the second signalis a negative voltage.
 7. An integrated circuit, comprising thereon: abond pad; a device identification circuit coupled to the bond pad andcomprising a resistor connected between a diode-connected transistor anda first reference voltage, wherein the diode-connected transistor has afirst polarity relative to the first reference voltage; and atemperature sensor diode coupled to the bond pad and in parallel withthe device identification circuit and having a second polarity relativeto a second reference voltage, the second polarity being different thanthe first polarity.
 8. The integrated circuit of claim 7, wherein theintegrated circuit comprises an image sensor.
 9. The integrated circuitof claim 7, wherein the first and second reference voltages are the samevoltage.
 10. The integrated circuit of claim 9, wherein the first andsecond reference voltages are ground.
 11. A system for identifying adevice and to measure its temperature, the system comprising: a powersupply; a common node coupled to the power supply; adevice-identification circuit coupled to the common node; and atemperature sensor in parallel with the device-identification circuitand coupled to the common node; the device-identification circuitconfigured to be placed in an ON state in response to a first voltageand the temperature sensor being configured to be placed in an OFF statein response to the first voltage; and the temperature sensor configuredto be placed in an ON state in response to a second voltage and thedevice-identification circuit being configured to be placed in an OFFstate in response to the second voltage; wherein the first and secondvoltages are of different polarity.
 12. The system of claim 11, whereinthe device identification circuit includes a diode-connected transistorconnected to a resistor with the diode-connected transistor having afirst polarity and connected to the common node and the resistorconnected between the diode-connected transistor and a first referencevoltage.
 13. The system of claim 12, wherein the temperature sensor is adiode having a second polarity.
 14. The system of claim 12, wherein thetemperature sensor is coupled between the common node and a secondreference voltage.
 15. The system of claim 14, wherein the first andsecond reference voltages are the same voltage.
 16. The system of claim15, wherein the first and second reference voltages are ground.
 17. Thesystem of claim 11, further comprising a second resistor connectedbetween the power supply and the common node.
 18. The system of claim17, wherein the power supply and the second resistor are disposed in animage-capture device.
 19. The system of claim 18, wherein the deviceidentification circuit and the temperature sensor diode are disposed inan image sensor.
 20. The system of claim 11, further comprising: aprocessor connected to the integrated circuit; a memory connected to theprocessor; and a driver circuit connected to the processor and to theintegrated circuit.
 21. The system of claim 20, wherein the memorycontains a look-up table relating different resistance values toassociated devices, the processor being configured to identify thedevice based on a substantial match between a value in the look-up tableand a value of the identification-circuit resistor.
 22. The system ofclaim 20, wherein the memory contains a look-up table relating differentvalues of an electrical parameter of the temperature sensor toassociated temperatures, the processor being configured to identify adevice temperature based on a substantial match between a present valueof the electrical parameter and a value in the look-up table.
 23. Thesystem of claim 22, wherein the sensor comprises a diode and theelectrical parameter is current through the diode.
 24. The system ofclaim 22, wherein the sensor comprises a diode and the electricalparameter is voltage across the diode.